Self Assessment Tax Calculator
Estimate your income tax and National Insurance for the 2026/27 tax year. Enter your gross self-employment income and allowable expenses to get a breakdown of your tax liability and estimated take-home pay.
This is an estimate only — always consult a qualified accountant for your actual tax return.
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How to use this self assessment calculator
Estimate your Income Tax and National Insurance contributions based on your self-employed income. Uses current HMRC tax bands for the 2026/27 tax year.
- 1Enter your annual income
Type your total self-employed income before any deductions.
- 2Add allowable expenses
Enter your business expenses to reduce your taxable profit.
- 3Select the tax year
Choose the correct tax year for your calculation.
- 4Review your breakdown
See your Income Tax, Class 2 and Class 4 NI, and take-home pay.
Why this matters
Every self-employed tradesperson in the UK must file a Self Assessment tax return by 31 January. Knowing your likely tax bill in advance helps you set aside the right amount each month, avoiding a nasty surprise when the deadline arrives.
Frequently asked questions
Who needs to submit a self-assessment tax return?
You must submit a self-assessment return if you are self-employed (even as a sole trader), a partner in a business partnership, a company director, or have other untaxed income (such as rental income or savings interest) above the relevant thresholds. HMRC requires you to register by 5 October of the tax year following the one you need to report.
What income tax rates apply to self-employed income in 2026/27?
For England, Wales and Northern Ireland: the personal allowance is £12,570 (income below this is tax-free); the basic rate of 20% applies to income from £12,571 to £50,270; the higher rate of 40% applies from £50,271 to £125,140; and the additional rate of 45% applies above £125,140. Note that the personal allowance is tapered by £1 for every £2 of income above £100,000.
What National Insurance do self-employed people pay?
Most self-employed people now pay only Class 4 NI: 6% on profits between £12,570 and £50,270, and 2% on profits above £50,270. Class 2 NI is no longer a mandatory charge — since April 2024, if your profits are above the £12,570 threshold you are treated as having paid it and receive the National Insurance credit for free. Anyone with profits below the Small Profits Threshold (£7,105 for 2026/27) can still pay voluntary Class 2 at £3.65 per week to protect their State Pension record.
How do I reduce my self-assessment tax bill?
The most effective way is to claim all legitimate business expenses — tools and equipment, vehicle costs (mileage or actual costs), home office costs, professional subscriptions, training, insurance, and more. Keeping accurate records of expenses throughout the year using software like InvoiceAdept makes this much easier at tax time.
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